Method and plant for manufacturing a belt structure, a belt package, and a crown structure for a vehicle tire

ABSTRACT

A method for manufacturing a vehicle-tire belt structure includes preparing half-strips; splicing respective half-strips to form belt strips; moving the belt strips toward at least one assembly drum; and superposing portions of the belt strips to form a belt structure. Related methods for manufacturing vehicle-tire belt packages and crown structures are also disclosed. A plant for manufacturing a vehicle-tire belt structure includes an extrusion apparatus to form a fabric sheet; means to transport the sheet; a device for cutting the sheet to form multiple strips; a device for preparing first and second half-strips; means for transporting the half-strips; a device for splicing the first half-strips and the second half-strips to form belt strips; a device for cutting the belt strips into portions; and at least one assembly drum adapted to support the portions. Related plants for manufacturing vehicle-tire belt packages and crown structures are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage entry under 35 U.S.C. § 371 fromInternational Application No. PCT/EP01/07313, filed Jun. 27, 2001, inthe European Patent Office, the contents of which are relied upon andincorporated herein by reference; additionally, Applicant claims theright of priority under 35 U.S.C. § 119(a)–(d) based on patentapplication No. 00202280.4, filed Jun. 29, 2000, in the European PatentOffice; further, Applicant claims the benefit under 35 U.S.C. § 119(e)based on prior-filed, copending provisional application No. 60/216,495,filed Jul. 6, 2000, in the U.S. Patent and Trademark Office.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In a first aspect thereof, the present invention relates to a method formanufacturing a belt structure of a green tire for vehicles.

This invention also refers to a plant for manufacturing the beltstructure, a method and a plant for manufacturing a belt package of agreen tire incorporating the above-mentioned belt structure, as well asa method and a plant for manufacturing a crown structure of a green tireincluding the above-mentioned belt package.

2. Description of the Related Art

As is known, a green tire is essentially constituted by a compositestructure obtained by assembling together a plurality of semi-finishedproducts adapted to constitute a carcass comprising at least oneairproof liner, a reinforcing ply, two bead wires to which the ply edgesare associated after interposition of an elastomeric filling fixed tothe radially outer surface of each bead wire, a belt structure arrangedas a crown around the torically shaped carcass, a tread wrapped aroundthe belt and a pair of axially opposite sidewalls, radially extendingbetween the bead wires and the tread.

A further layer incorporating a plurality of circumferentially orientedreinforcing cords, otherwise known as zero degree cords, may be insertedbetween the belt structure and the tread.

In the following description and in the subsequent claims, the term“belt structure” is used to indicate a composite structure including atleast a couple of radially superposed belt strips, provided withreinforcing cords parallel to one another in each strip and inclinedwith respect to the cords of the adjacent strip generally in asymmetrical manner with reference to the equatorial plane of the beltstructure.

In the following description and in the subsequent claims, the term“belt package” is used to indicate the assembly constituted by a beltstructure and an additional radially outer layer incorporatingcircumferentially oriented reinforcing cords.

Finally, in the following description and in the subsequent claims, theterm “crown structure” is used to indicate a composite structureconstituted by a belt package and a tread in its turn arranged as acrown around the additional layer of reinforcing strips of the beltpackage.

In the field of tire manufacturing, one of the requirements to besatisfied is notoriously that of imparting to the finished product highquality and long lasting characteristics, achieving at the same time ahigh production capacity of the manufacturing plant as a whole. In thisconnection, a critical factor which sharply influences the quality ofthe finished tire is constituted by the quality of the semi-finishedproducts which form the tire structure once they have been assembledtogether.

The quality of the semi-finished products is in turn linked to theproduction methods and to the environmental conditions in which thesemi-finished products are produced and optionally stored.

According to the state of the art, in the manufacturing of the beltpackage of the green tire, both the belt strips and the rubber mixtureribbon (or tape) incorporating the zero degree cords forming theabove-mentioned additional reinforcing layer, are wound around spools toform overlapping layers and are subsequently stored until they have tobe used in the production line and assembled on an assembly drum.

A first problem connected to this type of handling of the semi-finishedproducts is essentially linked to possible variations of the adhesion,of the chemical-physical characteristics and of the dimensionalcharacteristics of the semi-finished products, which take place bothduring the storing period and during the various handling steps whichsuch semi-finished products undergo before being used in the productionline.

During the storing period in which they are kept in spools, in fact, achange of the humidity and temperature conditions of the storingenvironment from those considered to be optimal may lead to an unwantedvariation of the rubber stickiness, generally a reduction of the same,which makes in some cases numerous layers of the semi-finished productunusable with an ensuing waste of material.

A second problem connected to the methods of handling and storing theabove-mentioned semi-finished products consists in the possibleappearance of undesired deformations and stresses due to the weight ofmaterial, which generally determines a compression of the radiallyinnermost layers of material in the spool, which compression influencesin turn the quality of the final product in a negative manner. In theworst cases, such compression of the layers may cause the rejection ofthe material which may no longer be used.

Another problem related to the above-mentioned handling methods of thesemi-finished products, in particular of the belt structure, of thelayer incorporating the zero degree cords and of the tread, consists inthe need to carry out a series of cumbersome operations of loading andunloading of the spools in the assembling machine, which require both acontinuous need for labor intervention and continuous stops, all this tothe detriment of the quality of the final product and of theproductivity of the plant used for manufacturing the green tire.

SUMMARY OF THE INVENTION

The technical problem underlying the present invention is therefore thatof providing a method and a plant for manufacturing a belt structure, abelt package and a crown structure of a green tire which enable theachievement both of the desired high and constant quality of the beltstructure, of the belt package, of the crown structure and of thesemi-finished products that constitute the same, and of a productivityincrease of the global plant.

According to a first aspect of the invention, the above-mentionedtechnical problem is solved by a method for manufacturing a beltstructure of a green tire for vehicles, comprising the steps of:

-   a) preparing, in a substantially continuous manner, a plurality of    half-strips having a predetermined length, aligned along respective    conveying directions and incorporating reinforcing cords    substantially parallel to one another in each half-strip;-   b) butt splicing, in a substantially continuous manner, said aligned    half-strips, so as to obtain respective belt strips extending along    said conveying directions;-   c) supplying, in a substantially continuous manner, said belt strips    to at least one assembly drum;-   d) superposing on said at least one assembly drum portions having a    predetermined length of each of said belt strips, so as to obtain a    belt structure comprising radially superposed strips in which said    reinforcing cords are parallel to one another in each strip and    inclined in opposite direction with respect to the cords of the    adjacent strip.

In the following description and in the subsequent claims, the term“length of the half-strips” is used to indicate the dimension of thehalf-strips measured in a direction parallel to the conveying directionsof the half-strips.

In the following description and in the subsequent claims, the term“width of the half-strips” is used to indicate the dimension of thehalf-strips measured in a direction perpendicular to the conveyingdirections of the half-strips.

In the following description and in the subsequent claims, theexpression “in a substantially continuous manner” is used to indicatethe absence of intermediate storages of the semi-finished productsbetween the various manufacturing steps which may change thechemical-physical and/or structural characteristics thereof in anundesired manner.

As an example, the expression “to prepare in a substantially continuousmanner a plurality of half-strips” is used to indicate that thehalf-strips are produced and subsequently processed, i.e. butt spliced,without the introduction of an intermediate storage between theirproduction and their subsequent butt splicing.

Advantageously, thanks to the realization of the belt strips in asubstantially continuous manner and immediately upstream of an assemblydrum, the method of the present invention enables not only to improvethe product quality and the process productivity, but also to reduce thestorage space and costs, as well as the material handling and laborcosts with respect to the methods of the prior art.

Preferably, the method of the invention comprises the step of preparing,in a substantially continuous manner, a plurality of half-strips.

In this way, it is advantageously possible to prepare, in asubstantially continuous manner and without any labor intervention, thehalf-strips intended to be spliced to each other to continuously formthe belt strips.

According to a preferred embodiment of the invention, the half-stripsare butt spliced on respective conveying means, arranged along theconveying directions of the half-strips, which conveying means may beconstituted by conveyor belts, rolls, mobile tables or any other meansknown in the art and suitable for the purpose.

According to the method of the invention, the desired belt structure,comprising the radially superposed strips incorporating reinforcingcords parallel to one another in each strip and inclined in oppositedirection with respect to the cords of the adjacent strip with referenceto the center-line plane of the belt structure, can be obtained in twodifferent ways.

In a first embodiment, the method of the invention provides for theformation, upstream of the assembly drum, of two belt stripssubstantially parallel to one another and already having the desiredopposite inclination of the reinforcing cords with respect to theconveying direction of the half-strips structurally independent from oneanother and to the conveying direction of the belt strips obtained bysplicing the half-strips.

According to such embodiment, the method of the invention comprises thestep of turning each of the half-strips upside down, which half-strips,once butt spliced, form one of the belt strips.

The superposing step of the belt strips on the assembly drum istherefore carried out by tangentially feeding the strips either both atthe top or both at the bottom of the assembly drum, which is rotated inthe same direction during the winding of each strip.

In a second embodiment, the method of the invention provides for theformation, upstream of the assembly drum, of two belt stripssubstantially parallel to one another in which the reinforcing cordshave the same inclination with respect to the conveying direction of thehalf-strips structurally independent from one another and to theconveying direction of the belt strips obtained by splicing thehalf-strips.

In this case, the superposing step of the belt strips on the assemblydrum is carried out by tangentially feeding each strip, respectively oneat the top and one at the bottom of the assembly drum, which is rotatedin opposite directions during the winding of each strip.

Preferably, the belt strips are fed to the assembly drum by means of theabove-mentioned conveying means.

In a preferred embodiment of the invention, the step of superposing theportions of each belt strip on the assembly drum is carried out by usinga couple of assembly drums.

In this way, it is advantageously possible to increase the productionrate of the plant for carrying out the method of the invention byreducing the time of each assembling cycle of the belt structure. Itshould be observed that the belt strips which constitute the beltstructure, once they have been superposed on one another on the assemblydrum, have a different circumferential development. It follows that oneof the belt strips, and precisely the radially outer one, is used morethan the other one. In order to take account of such different use ofthe two strips, it is convenient and preferable to discard, as afunction of the material in excess detected by suitable sensors, one ofthe half-strips intended to constitute the radially inner belt strip. Inany case, the amount of discarded material generated by said steps ofthe method of the invention (steps carried out in a substantiallycontinuous manner and immediately upstream of the assembly drum) ishowever lower than the amount of discarded material normally generatedby the production methods of the prior art and due to the aforementionedcompression and mutual adhesion phenomena of the belt layers wound onthe storing spool.

For the implementation of the above-mentioned method, the presentinvention provides a plant for manufacturing a belt structure of a greentire for vehicles.

According to a preferred embodiment, the plant of the present inventionprovides a butt splicing device of the structurally independenthalf-strips, which operates substantially by applying pressureperpendicularly to the surface of the half-strips to be spliced.

Advantageously, such a device reduces almost to zero the damagingstrains exercised in longitudinal direction on the half-strips, whichmay cause undesired deformations of the latter.

In this embodiment, it is preferable to extrude the initial sheet ofrubber-coated fabric incorporating the reinforcing cords in such a wayas to provide the same with a lateral lip constituted by elastomericmaterial. In the subsequent operative steps of forming the half-stripsstarting from the initial sheet of rubber-coated fabric, said lip ispositioned at one of the splicing edges of the half-strips and defines aseat for receiving with substantial mating engagement the end of theadjacent half-strip.

In this embodiment, the splicing device comprises a plate of suitableweight and size, movably supported above the conveying means of thehalf-strips, which plate promotes—by pressing each half-strip—theadhesion between one end of the half-strip and the underlying lip of theadjacent half-strip previously incorporated in the belt strip beingformed.

Alternatively, the splicing device may comprise a plurality ofcounter-rotating upper and lower rolls supported above and,respectively, below the conveying means of the half-strips, said rollstraveling along a direction parallel to the edges of the half-strips tobe spliced.

Alternatively, the splicing device may be of the comb-type, i.e.including a plurality of jaws adapted to grasp the edges of the adjacenthalf-strips to carry out the butt splicing thereof along a directionparallel to the longitudinal direction of the half-strips.

The plant of the invention enables the preparation of a belt structureof a green tire in a totally automated manner, limiting as much aspossible the labor involved and without any need to store thesemi-finished products, which are advantageously produced immediatelybefore being assembled together to form the belt structure.

With the plant of the invention, the risks of quality variations of thebelt structure related to possible variations of the chemical-physicalcharacteristics of the semi-finished products and/or related to avariation of temperature and/or humidity of the warehouse or to a longpermanence of the semi-finished products on the spools are alsoadvantageously reduced to a minimum or substantially eliminated.

In a preferred embodiment, the plant of the invention is provided withan extrusion apparatus comprising an extrusion head adapted to supply ina substantially continuous manner a substantially continuous sheet ofrubber-coated fabric incorporating a plurality of reinforcing cords onsaid conveying means, said plurality of reinforcing cords being suppliedby a creel located upstream of said extrusion head.

Downstream of this extrusion apparatus, the plant according to theinvention comprises a first cutting device operating on said sheet ofrubber-coated fabric and adapted to obtain a plurality of strips fromthis sheet.

Preferably, the plant of the invention also comprises a half-stripspreparation device including a transfer device of the strips obtained asdescribed above, which transfer device is adapted to move the stripsaway from the conveying direction of the sheet of rubber-coated fabric,a second cutting device operating on said strips and adapted to form aplurality of half-strips, and a positioning device of the half-strips.

Advantageously, thanks to said features, the plant lay-out turns out tobe independent from the cutting angle of the strips, so that a reductionin the area occupied by the plant is achieved with respect to the plantsof traditional type; furthermore, the production of the strips turns outto be independent also from the cutting and positioning operations ofthe half-strips, maximizing in this way the plant productivity.

An additional advantage achieved by the invention consists in theincrease of the production flexibility, with particular reference to thereduction in the time required to shift to a production of tires ofdifferent size, the operations required being limited—if it is notrequired to change the type of cord—only to the variation of the cuttingangle of the sheet of rubber-coated fabric and/or to the cutting of astrip of a different length.

Furthermore, with respect to the prior art systems based on the use ofbelt strips prearranged and packed on spools, it is not necessary tostore and handle the spools as well as the various supporting fabricsused, such as the sheets of release material (for example polyester orpolyethylene) coupled to the belt strip before carrying out its windingon the spool.

In a preferred embodiment, the transfer device comprises at least onestrip-supporting arm angularly movable between a first strip-receivingposition located downstream of said first cutting device of the sheet ofrubber-coated fabric and a strip picking-up position.

According to a preferred aspect, the supporting arm is provided with astrip-supporting oscillating table hinged to said arm and movable to andfrom said first cutting device.

In an alternative embodiment, the transfer device comprisesstrip-conveying means, for example a conveyor belt or any other kind ofmeans having the same function, having a conveying axis which issubstantially parallel to the cutting direction of the sheet ofrubber-coated fabric and movable between the above-mentioned firststrip-receiving position located downstream of the first cutting deviceand said strip picking-up position.

In a preferred embodiment, the half-strips preparation device of theinvention comprises a positioning device of the half-strips adapted topick up each of the strips from said strip picking-up position, to placethe same in the aforesaid strip cutting position and to subsequentlymove the half-strips so obtained away from each other.

Conveniently, the positioning device of the half-strips is provided withcatching means of the strip rotatably mounted about an axisperpendicular to the strip in such a way as to rotate each strip, ifnecessary, of a third predetermined angle with respect to the conveyingdirection of the sheet of rubber-coated fabric.

Preferably, the catching means of the strip are mounted on a supportingframe movably guided to and from the strip to be positioned.

Even more preferably, the positioning device of the half-strips isprovided with two coplanar plates, each provided with strip catchingmeans, which plates are driven away and towards each other.

Advantageously, such coplanar plates operate along a direction parallelto the upper face of the strip, therefore avoiding the creation ofundesired stresses in the material making up the strip such as thestresses produced when the strip is handled by grasping the same by itsedges with subsequent undesired strains, especially in longitudinaldirection.

In an alternative embodiment, the half-strips preparation device issubstantially constituted by the second cutting device and by thepositioning device of the half-strips, which picks up each strip fromthe above-mentioned strip-receiving position and places the samedirectly in the second strip cutting position to form said half-strips.

In an embodiment of the plant and consistently with the method accordingto which the belt strips possess the required opposite inclination ofthe reinforcing strips already upstream of the assembly drum, thehalf-strips preparation device further comprises an upturning device ofone of the half-strips, which is placed downstream of the second cuttingdevice and upstream of the conveying means of one of the half-strips.

Preferably, the upturning device includes a plate provided with catchingmeans of the half-strip, said plate being rotatably mounted on arespective supporting frame which is guided to and from the conveyingmeans of the half-strip which is thus turned upside down.

According to a further aspect of the invention, the above-mentionedtechnical problem is solved by a method for manufacturing a belt packageof a green tire for vehicles.

In an embodiment, the width of the layer incorporating the zero degreereinforcing cords may substantially be equal to the width of the beltstructure, whereas its length is substantially equal to thecircumferential development of the assembly drum.

Conveniently, means capable of applying a suitable pressure on the treadare used during the application of the tread on the belt package, inorder to increase the adhesion of the tread to the belt packageunderneath and to strengthen the assembly thereof.

In a preferred embodiment, the layer incorporating the zero degreereinforcing cords may be formed by spirally winding around the beltstructure at least one relatively narrow ribbon of rubber mixture,subsequently referred to as: tape, incorporating one or more reinforcingcords. Conveniently, this tape is wound in such a way as to obtainaxially aligned spirals circumferentially extending around the bellstructure substantially along its entire width.

For the implementation of the above-mentioned method for manufacturing abelt package of a green tire for vehicles, the invention provides aplant.

Preferably, the plant for manufacturing the belt package is providedwith an extrusion apparatus, including an extrusion head, adapted toform in a substantially continuous manner the ribbon (or tape) of rubbermixture incorporating the zero degree reinforcing cords.

According to a further aspect of the invention, the above-mentionedtechnical problem is solved by a method for manufacturing a crownstructure of a green tire for vehicles.

In a preferred embodiment, the tread is formed in a substantiallycontinuous manner by extrusion.

For the implementation of the above-mentioned method for manufacturingthe crown structure of a green tire for vehicles, the invention alsoprovides a plant.

According to the invention, said plant comprises an extrusion apparatusfor supplying a continuous tread sheet of rubber mixture from which thetreads required for completion of the crown structure are produced, aswell as conveying means for transferring said continuous tread sheet ofrubber mixture towards an assembly drum, on which the previously formedbelt package is supported.

Preferably, the above-mentioned conveying means of the continuous treadsheet of rubber mixture are provided with cooling means, for examplewith a set of serpentine tubes in which cold water circulates.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional features and advantages of the invention will become morereadily apparent from the description of some embodiments of a methodfor manufacturing a belt structure, a belt package and a crown structureof a green tire according to the invention, made with reference to theattached drawing figures in which, for illustrative and non limitingpurposes, a plant for carrying out said method is shown.

In the drawings:

FIG. 1 schematically shows a plant for manufacturing a crown structureaccording to the present invention;

FIG. 2 is a schematic top view, in an enlarged scale, of a half-stripspreparation device intended for forming a first and a second belt strip;

FIG. 3 schematically shows, in an enlarged scale, some details of thehalf-strips preparation device of FIG. 2;

FIGS. 4, 5, and 6 are schematic views of respective operative conditionsof catching means of a continuous sheet of rubber-coated fabric providedfor upstream and cooperating with the half-strips preparation device ofFIG. 2;

FIG. 7A is an elevational view of a strip transfer device, a secondcutting device, and a positioning device of the half-strips which arepart of the half-strips preparation device of FIG. 2;

FIG. 7B is an elevational view of the positioning device of thehalf-strips of FIG. 7A and a collection container of the half-strips inexcess;

FIG. 8 is an elevational view of the positioning device of thehalf-strips of FIG. 7A and of a half-strip upturning device cooperatingwith the same;

FIGS. 9, 10, and 11 are elevational views of the half-strip upturningdevice of FIG. 8 in respective operative conditions thereof;

FIG. 12 is a schematic perspective view of the conveying and cuttingmeans of the belt strips and a pair of assembly drums;

FIG. 13 is an elevational view of a device for supporting and angularlypositioning the assembly drums of FIG. 12;

FIG. 14 is a schematic top view, in an enlarged scale, of an alternativeembodiment of the half-strips preparation device intended for formingthe belt strips;

FIGS. 15 and 16 are schematic views of operative conditions of catchingmeans of a continuous sheet of rubber-coated fabric provided forupstream and cooperating with the half-strips preparation device of FIG.14;

FIG. 17 is a schematic top view of the catching means illustrated inFIGS. 15 and 16;

FIG. 18 is an enlarged scale partial schematic view of the belt strip,illustrating the butt splicing between adjacent half-strips at a lipextending from one of the latter;

FIG. 19 is a schematic elevational view of a preferred embodiment of asplicing device of the half-strips and a conveyor belt for conveying thebelt strip obtained by the above-mentioned half-strips;

FIG. 20 is a schematic perspective view of an alternative embodiment ofthe conveying and cutting means of the belt strips and of a pair ofassembly drums; and

FIG. 21 is an elevational view of a device for supporting and angularlypositioning the assembly drums of FIG. 20.

DETAILED DESCRIPTION OF THE EMBODIMENTS

With reference to the schematic lay-out of FIG. 1, a plant according tothe invention for manufacturing, in a substantially continuous manner, acrown structure of a green tire for vehicles is generally indicated at1. The plant 1 comprises a plant 2 for manufacturing, in a substantiallycontinuous manner, a belt structure, a production line 3 formanufacturing, in a substantially continuous manner, a ribbon 103 oflimited width (tape) of rubber mixture comprising a plurality ofreinforcing cords 104 and a production line 4 for manufacturing, in asubstantially continuous manner, a tread 105.

In the illustrated example, the plant 2 comprises an extrusion apparatus5, aimed at forming, in substantially continuous manner, a sheet 109 ofrubber-coated fabric incorporating a plurality of reinforcing cords 106substantially parallel to one another. The extrusion apparatus 5 is fedby a creel 6 which supplies the cords 106, made of a suitablereinforcing material, for example metal cords, to an extrusion head 7positioned downstream of the creel 6 and to a comb-type device 6 b iswhich sets the coplanarity and the parallelism of the cords 106;additionally, the extrusion head 7 is fed by a rubber mixture ofsuitable composition by means of an extrusion screw 47, conventional perse.

Immediately downstream of the extrusion head 7, conveying means 8 of thesheet 109 of rubber-coated fabric are provided, for example constitutedby a conveyor belt, which means convey the sheet 109 of rubber-coatedfabric along a predetermined conveying direction X—X (see FIG. 2)towards a half-strips preparation device, generally indicated at 9,which will be described in greater detail in the following withreference to FIGS. 2–6.

A first cutting device 32, schematically shown in FIGS. 1, 2 and 5, isprovided upstream of the half-strips preparation device 9 for cuttingthe sheet 109 of rubber-coated fabric along a cutting direction forminga predetermined angle α with respect to the above-mentioned conveyingdirection X—X, so as to obtain a sequence of strips 108 having apredetermined length and aligned along said direction X—X.

Preferably, said angle α is comprised between 18° and 30° depending uponthe size and the type of performance of the tire to be produced.

The main function of the half-strips preparation device 9 is that ofsplitting the strips 108, obtained from the sheet 109 of rubber-coatedfabric, into a first plurality of half-strips 107 and into a secondplurality of half-strips 110, aligned along respective conveyingdirections Y—Y and Z—Z.

To this end, the half-strips preparation device 9 comprises a transferdevice, generally indicated at 27, to move each strip 108 away from astrip-receiving position C located downstream of the first cuttingdevice 32 along the conveying direction X—X of the sheet 109 ofrubber-coated fabric and to place the strip at a cutting position F,away from said direction X—X, adapted to readily enable the subsequentforming operations of the half-strips 107 and 110.

In particular, respective catching means 50 of the sheet 109 ofrubber-coated fabric are provided upstream of the transfer device 27,which catching means are constituted in the illustrated example by amovable plate parallel to the conveyor belt 8 and provided with magnets56, adapted to drag the sheet 109 of rubber-coated fabric away from theconveyor belt 8 and past the first cutting device 32 for a portionhaving a length equal to the length of the strip to be produced.

The catching means 50 may include, instead of the magnets 56, suitablemeans adapted to hold the sheet material such as a plurality of suctioncups connected to a vacuum pump, particularly suitable when the cords106 are made of a non-magnetic material, for example textile fiber.

In the subsequent description, for illustrative and non limitingpurposes, magnetic catching means will be described.

In a first embodiment of the plant 2, the transfer device 27 comprises amultiple arm carousel 57 including four strip-supporting arms, allindicated at 28, angularly spaced of 90° from one another andcantilevered from a rotating support 48 driven by respective motor means49.

This carousel 57 cooperates with a plate 50 which releases the strip108, obtained from the first cutting device 32, down onto one of theaforementioned arms 28 placed in the strip-receiving position Csubstantially aligned with the conveyor belt 8 (i.e. with the conveyingdirection X—X); subsequently, the multiple arm carousel 57 places saidarm with the relative strip 108 deposited thereon in a picking-upposition E away from direction X—X and places a new arm 28 in thereceiving position C for receiving a subsequent strip.

In order to simplify these transfer operations of the strips 108, eachof the above-mentioned arms 28 may be provided on top with anoscillating table 31 (FIGS. 4–6) hinged thereto and driven by respectivemotor means of conventional type, not shown.

The oscillating table 31 rotates to and from the strip-receivingposition C provided downstream of the first cutting device 32 andadvantageously avoids any possible interference between the arms 28 andthe conveyor belt 8.

In a preferred embodiment, the half-strips preparation device 9comprises a positioning device 33 of the half-strips, adapted to pick upeach strip 108 from the arm 28 at the picking-up position E and placethe picked up strip 108 at an appropriate cutting position F wherein asecond cutting device 34 is arranged.

If necessary, the positioning device 33 of the half-strips also rotatesthe strip 108 of a predetermined angle γ.

In the embodiment illustrated in the figures, in which the picking-upposition E of the strips 108 forms an angle of 90° with the conveyingdirection X—X of the sheet 109 of rubber-coated fabric, the angle γ iscomprised between 60° and 72°.

More particularly, the positioning device 33 of the half-strips placesthe strip 108 with respect to the second cutting device 34 at a positionF in such a way that the cutting of the strip 108 occurs along adirection forming a predetermined angle β with respect to thelongitudinal axis I—I of the strip 108.

Said angle β is equal to the strip cutting angle α and is comprisedbetween 18° and 30° depending upon the size and the type of performanceof the tire to be produced. In this way, the cutting direction of eachstrip 108 is substantially parallel to the sides of the strip 108 a, 108b which are longitudinally opposed along the direction of thereinforcing cords (FIG. 3).

Advantageously, thanks to the cooperation between the multiple armcarousel 57 and the positioning device 33 of the half-strips, the cycletime required to pick up each strip from the strip-receiving position Cand to place the strip in the strip cutting position F is reduced,resulting in an increase of the plant productivity.

In a further embodiment, not shown, the carousel 57 may not be present:in this case, the positioning device 33 of the half-strips directlypicks up the strip 108 from position C and subsequently places the sameat the cutting position F.

At the cutting position F, the second cutting device 34 cuts each strip108 in two half-strips having an appropriate width according to theoffset to be given to the edges of the radially superposed belt strips.

In this preferred embodiment, the positioning device 33 of thehalf-strips is provided both with means suitable to pick up andtransport the strip 108, and with means capable of positioning each ofthe half-strips 107 and 110 obtained by cutting the strip 108.

More particularly, the positioning device 33 of the half-stripscomprises catching means 36 which are rotatably mounted on a supportingframe 37 guided to and from the second cutting device 34 and driven byrespective motor means 43. In the example illustrated in FIGS. 7A, 7Band 8, the catching means 36 of the strips 108 of the positioning device33 of the half-strips is constituted by a pair of coplanar plates 38 aand 38 b, for example of magnetic type, respectively supported by twoslides 64 a and 64 b, slidably mounted on a supporting beam 65 anddriven by a motor 66. The supporting beam 65 and the catching means 36slidably mounted thereon are rotated about an axis P—P by a motor 72positioned on a support 61 fixed to the frame 37 (see FIGS. 7A and 7B).

The displacement of the slides 64 a and 64 b enables to move the plates38 a and 38 b away and towards each other along a horizontal directionsubstantially perpendicular to the cutting direction.

The frame 37 is in turn associated to a supporting trolley 58 moved byrespective motor means 44 along an overhead track 45, forming a closedloop and supported in a conventional manner known per se above thehalf-strips preparation device 9.

In this way, the positioning device 33 of the half-strips may travelalong a closed loop-shaped circuit and may be transferred from the stripcutting position F to a releasing position of the half-strips 107 and110 on respective devices for their further processing as will bedescribed further on.

As already explained, the half-strips preparation device 9 illustratedin FIGS. 2 and 3 and comprising a plurality of positioning devices 33 ofthe half-strips, advantageously increases the production capacity of theplant 2.

The second strip cutting device 34, adapted to cut each strip 108 alongthe above-mentioned cutting direction, is schematically shown in FIGS.7A and 7B.

Preferably, the cutting device 34 includes a system known in the artwith the term “slitter” including two counter-rotating disks 34 a and 34b, peripherally provided with a cutting edge, which disks are driven bya motor 35 along the cutting direction of the strip 108.

In the example illustrated and as already anticipated, the positioningdevice 33 of the half-strips advantageously rotates the strips 108 intheir lying plane before carrying out their cutting, and places thehalf-strips 107 and 110, suitably moved away from one another,respectively on a conveyor belt 11 having a conveying axis Y—Y, or onanother suitable conveying means, and on an upturning device 10.

In a preferred embodiment, the conveyor belt 11 and the upturning device10, positioned immediately downstream of the second cutting device 34supported at the cutting position F, are substantially parallel to theconveyor belt 8 of the initial sheet 109 of rubber-coated fabric inorder to limit the size of the plant.

The upturning device 10 of the half-strip 110 exerts the function ofturning one of the half-strips upside down, in this case the half-strip110, in such a way that the reinforcing cords 106 thereof turn out to besymmetrically inclined with respect to those of the other half-strip(indicated at 107) with respect to the cutting direction of the strip108.

In the example illustrated, the upturning device 10 comprises a plate 39provided with suitable catching means, for example of magnetic type(FIGS. 8–11).

The plate 39 is rotatably mounted on a supporting frame 40 and isrotated around its transversal axis by respective motor means 51 towhich the plate 39 is kinematically connected in a manner known per se.

The plate 39 is also associated to a supporting trolley 59 associated tothe frame 40, which travels on the frame 40 along a vertical directiondriven by respective motor means 52.

In this way, the trolley 59 and the plate 39 associated thereto can movevertically to and from a conveyor belt 12 positioned under the upturningdevice 10 and intended to receive and convey the half-strip 110 along aconveying direction Z—Z once the half-strip has been turned upside down.

In this way, a first and a second plurality of half-strips 107 and 110,aligned with one another and incorporating reinforcing cords 106substantially parallel to one another and symmetrically inclined withrespect to the conveying directions Y—Y and Z—Z of such conveyor belts,are placed on the conveyor belts 11 and 12 in a substantially continuousmanner.

Respective butt splicing devices of the half-strips 107 and 110,previously placed along the above-mentioned belts 11, 12 by thepositioning device 33 of the half-strips and, respectively, by theupturning device 10 are provided along each of the conveyor belts 11 and12.

Said splicing devices, of conventional type not shown, may comprise aplurality of upper and lower counter-rotating rolls, respectivelysupported above and below the conveyor belts 11 and 12, which splice byapplying pressure to the edges of adjacent half-strips or,alternatively, may comprise a plurality of jaws adapted to grasp theedges of the half-strips and splice the same by pressing them againsteach other.

Thus the above-mentioned splicing devices enable to obtain, startingfrom the aligned half-strips 107 and 110, respective belt strips 113 aand 113 b extending along the conveying directions Y—Y and Z—Z of theconveyor belts 11 and 12.

In a preferred embodiment, and as illustrated in FIG. 12, each of theconveyor belts 11 and 12 comprises two sections, respectively upstreamsections 11 a, 12 a and downstream sections 11 b, 12 b spaced from eachother to form respective spaces A, B adapted to contain a portion havinga predetermined length of each of the belt strips 113 a and 113 b, knownin the field with the term of “festoon”.

More particularly, the festoon formed by the belt strips 113 a and 113 bcarries out the advantageous function of storage unit adapted to absorbany possible different processing rates and/or use rates of thesemi-finished products upstream and downstream of the conveyor belts 11and 12.

In this embodiment, and in order to detect the length of theabove-mentioned festoons, the plant 2 of the invention advantageouslycomprises a plurality of sensors suitably positioned at the spaces A, Bhousing the festoons formed by the belt strips 113 a and 113 b.

In FIG. 12, the sensors 42 a and 42 b intended for controlling thelength of the festoon formed by the belt strip 113 a in space A can beseen.

Respective cutting devices, schematically indicated at 41 a and 41 b inFIG. 12, are positioned along the conveyor belts 11 and 12 downstream ofthe spaces A and B for cutting the belt strips 113 a, 113 b in portions112 a and 112 b having a predetermined length. In the illustratedexample, each of the two cutting devices 41 a and 41 b comprises ashearer of conventional type.

Finally, the plant 2 comprises a pair of assembly drums 13 and 14,placed immediately downstream of the conveyor belts 11 and 12 andintended to carry out the assembling step of the belt structure startingfrom the belt strip portions 112 a and 112 b thus formed on the conveyorbelts 11 and 12.

In the illustrated example, the drums 13 and 14 are coaxially alignedalong a rotation axis (A—A) and are placed on diametrically oppositesides of a device 15 for supporting and angularly positioning the drumswhich is driven by respective independent motor means 16 (FIG. 13).

Advantageously and as will be better apparent in the following, thedevice 15 switches the drums 13 and 14 with one another at the end ofeach assembling operation of a belt strip carried out thereon in orderto substantially reduce the assembling cycle time of the belt structurewith respect to a single drum.

In this embodiment, the belt structure is preferably assembled on thedrum 13 or 14 which is substantially aligned with the conveyor belt 12in a position referred to hereinbelow as assembling position. In thisembodiment, in fact, the belt strip 113 a is used to form the radiallyinner strip of the belt structure, whereas the belt strip 113 b is usedto form the radially outer strip of the belt structure.

As indicated above, the above-mentioned plant 2 for manufacturing thebelt structure of the green tire cooperates, within the area of theplant 1, with the production line 3 for preparing the tape 103incorporating the reinforcing cords 104 and with the production line 4for preparing the tread 105 to produce, respectively, the belt packageand the final crown structure.

To this end and as illustrated in FIG. 1, the plant 1 comprises a firsttransfer device 17, known per se and from now on indicated as a transferring, adapted to transfer the belt structure produced in the plant 2from the above-mentioned assembling position of the drums 13 and 14 ontoa third assembly drum 18 on which the crown structure is assembled.

Preferably, the assembly drum 18 has a rotation axis B—B substantiallyaligned with the rotation axis A—A of the drums 13 and 14 in order toreduce the overall size of the plant 1 and to facilitate the transferoperations of the belt structure.

Advantageously, the production line 3 of the tape 103 and the productionline 4 of the tread 105 are positioned in the plant 1 immediatelyupstream of the assembly drum 18, therefore avoiding any need to storethese semi-finished products.

The production line 3 of the tape 103 essentially comprises an extrusionapparatus 19, adapted to form, in a substantial continuous manner, anarrow ribbon of rubber mixture (the tape) incorporating a plurality ofreinforcing cords 104, as well as means to guide the tape produced inthis way towards the assembly drum 18. This means include cooling andstoring means, such as a set of rolls 23.

The extrusion apparatus 19 is fed by a creel 20 provided with aplurality of spools, all indicated at 21, which supplies the cords 104to an extrusion head 22 fed with a rubber mixture of suitablecomposition by means of a conventional extrusion screw 53 known per se.

Conveniently, the cords 104 are made of a suitable reinforcing material,for example a textile material, such as polyamide, or metal.

The assembly drum 18 is preferably equipped with means, conventional perse and not shown, adapted to facilitate the winding of the tape 103 onthe belt structure already prepared on the drum 18 (said means beingconstituted, for example, by one or more pressing rolls) and to cut thetape 103 once the latter has formed the reinforcing layer including thezero degree cords.

In an embodiment, this cutting means may be constituted by a knowncutting mechanism of the pneumatic shear type.

The production line 4 of the tread 105 comprises an apparatus 24,adapted to extrude or form, in a substantially continuous manner, atread sheet 114 of rubber mixture aimed at constituting the tread 105,as well as means for conveying the continuous tread sheet 114 towardsthe assembly drum 18, such as a conveyor belt 26.

The apparatus 24, which in the illustrated example includes an extrusionscrew and an extrusion head 25 of conventional type, only schematicallyrepresented, is fed by a rubber mixture of suitable composition.

Preferably, the conveyor belt 26 is provided with suitable coolingmeans, such as a set of serpentine tubes through which cold watercirculates, intended for cooling the continuous tread sheet 114 from thetemperature the sheet has when it leaves the extrusion or forming head(generally equal to approximately 80° C.) down to a temperature suitablefor carrying out the subsequent processing of the tread sheet 114(conveniently in the order of approximately 40–45° C.).

Cutting means, conventional per se and not shown, are also providedalong the conveyor belt 26 for cutting the continuous tread sheet 114 inportions having a predetermined length corresponding to thecircumferential development of the tread of the tire in production or toa submultiple thereof.

In this way, it is possible to obtain a set of treads 105 (illustratedin FIG. 1) aligned along the conveyor belt 26 immediately upstream ofthe assembly drum 18.

In an alternative embodiment of the method of the invention, each tread105 may be cut from the continuous tread sheet 114 during the windingoperations around the assembly drum 18 by means of conventional cuttingmeans known per se and not shown.

Similarly to what has been indicated above with reference to the tape103, the assembly drum 18 is preferably equipped with means,conventional per se and not shown, adapted to facilitate the applicationof each tread 105 as a crown around the reinforcing layer including thezero degree cords 104.

As an example, said means may be constituted by one or more pressingrolls acting on the tread 105.

Finally, the plant 1 includes a positioning device 46 for positioningthe assembly drum 18, adapted to move the drum by rotating the latter of180° about a vertical axis perpendicular to the rotation axis B—B of thedrum 18, from an assembling position (indicated at D in FIG. 1) of thecrown structure, to a picking-up position (indicated at G in FIG. 1,wherein the drum 18 is indicated by a dotted line) of said structure bya second transfer ring 60.

This second transfer ring 60 transfers the crown structure towards aso-called first phase assembling line, not represented, on which linethe cylindrical carcass sleeve adapted to be torically shaped andassembled with the crown structure is prepared.

With reference to the above-mentioned plant, a first embodiment of themethod according to the invention for manufacturing a belt structure ofa green tire comprises the following steps.

In a first step, the sheet 109 of rubber-coated fabric incorporating thereinforcing cords 106 is formed in a substantially continuous manner bymeans of the extrusion apparatus 5, which sheet—once it has left theextrusion head 7—is transported by the conveyor belt 8 towards the strippreparation device 9 along the conveying direction X—X.

In a subsequent step and immediately upstream of the half-stripspreparation device 9, the sheet 109 of rubber-coated fabric is picked upby the catching means 50 which places the same at the first cuttingdevice 32 that cuts the sheet 109 of rubber-coated fabric along adirection forming a predetermined angle α (for example equal toapproximately 30°) with respect to the conveying direction X—X.

In this way and as a result of subsequent cuts of the sheet 109 ofrubber-coated fabric, a plurality of strips 108 having a predeterminedlength, aligned with one another along the direction X—X, is obtained.

In a subsequent step, each strip 108 is transferred to a cuttingposition F away from the above-mentioned direction X—X by means of thestrip transfer device 27, for example by means of the multiple armcarousel 57 and of the positioning device 33 of the half-stripscooperating with the same.

In this embodiment, the one of the arms 28 of the multiple arm carousel57 which is located at the strip-receiving position C and which supportsthe strip 108 to be transferred, is rotated of approximately 90° towardsthe picking-up position E of the strip 108, position at which thepositioning device 33 of the half-strips intervenes.

The positioning device 33 picks up the strip 108 resting on the rotatedarm 28 (at picking-up position E) by means of the magnetic plates 38 aand 38 b and rotates the strip 108 of a predetermined angle γ withrespect to the direction X—X (for example equal to approximately 30°)until it brings the strip 108 to the required cutting position F.

Once the positioning device 33 of the half-strips has picked up thestrip 108, the multiple arm carousel 57 is further rotated of 90° so asto place other arms 28 respectively at the strip-receiving position Cand at the picking-up position E, thereby repeating the previouslydescribed operations.

In a subsequent step, the strip 108 held at the cutting position F bythe positioning device 33 of the half-strips is then cut in two parts bythe second cutting device 34 along a direction forming an angle β equalto the predetermined angle α (for example, 30°) with respect to thelongitudinal axis I—I of the strip.

In this way, two half-strips are obtained, respectively left 107 andright 110 with respect to the cutting direction, not necessarily of thesame width, in the sense that the half-strip which will constitute theradially inner belt strip of the tire (the half-strip 107, according tothe illustrated example) preferably has a width greater than the widthof the half-strip which will constitute the radially outer belt strip(the half-strip 110).

In a subsequent step, the half-strips 107 and 110 are suitably movedaway from each other along a direction substantially perpendicular tothe cutting direction by moving the plates 38 a and 38 b of thepositioning device 33 of the half-strips away from each other.

Subsequently, the half-strips 107 and 110 thus moved away are releasedby said device 33 onto the conveyor belt 11 and, respectively, onto theupturning device 10.

Once the half-strips 107 and 110 have been released, the positioningdevice 33 of the half-strips may move forward along the closedloop-shaped track 45 and return to the picking-up position E of a newstrip 108 so as to repeat the previously described operations.

In an additional step of this embodiment of the method according to theinvention, the half-strip 110 is taken, lifted and turned upside down bythe magnetic plate 39 of the upturning device 10 in such a way as toobtain an inclination of the reinforcing cords 106 symmetrical withrespect to that of the cords 106 of the half-strip 107 with reference tothe above-mentioned cutting direction of the strip 108.

After this upturning step of the half-strip 110, the magnetic plate 39is demagnetized in order to release the half-strip 110 turned upsidedown onto the conveyor belt 12 (FIGS. 9–11).

At the end of the above-mentioned steps, a plurality of first and secondhalf-strips 107, 110 are therefore obtained in a substantiallycontinuous manner, aligned with one another along the conveyor belts 11and 12 and incorporating respective reinforcing cords 106 symmetricallyinclined with respect to the conveying directions Y—Y and Z—Z of each ofthe above-mentioned belts 11 and 12.

In a further step of the method, said half-strips 107 and 110 are buttspliced to each other in order to form in a substantially continuousmanner respective continuous belt strips 113 a and 113 b extending onthe conveyor belts 11 and 12 along the above-mentioned conveyingdirections Y—Y and Z—Z.

The butt splicing between subsequent half-strips 107, 110 takes place byapproaching the edges of adjacent half-strips thanks to a pressureapplied, along the entire edge, by the splicing device, for example ofthe counter-rotating roll type, supported above and/or below theconveyor belts 11 and 12.

In the non limiting illustrated example, the belt strip 113 a formed onthe belt 11 is used to form the radially inner layer of the beltstructure, while the belt strip 113 b formed on the belt 12 is used toform the radially outer layer of the belt structure.

In a preferred embodiment, the method of the invention comprises theadditional step of discarding one of the half-strips 107 used to formthe radially inner belt strip 113 a on the basis of a signal sent by thesensors 42 a, 42 b delegated to detect the length of the festoon formedby said belt strip 113 a in the storage space A defined between thesections 11 a and 11 b of the belt 11.

Preferably, this discarding step is carried out by the positioningdevice 33 of the half-strips which, instead of releasing the half-strip107 in excess on the belt 11, holds the same on the magnetic plate 38 aand then releases the half-strip 107 into an appropriate collectioncontainer 67 out of line (FIG. 7B). Alternatively, and provided that thehalf-strips 107, 110 are of the same width, it is possible to avoid theelimination of the half-strip in excess by incorporating the twohalf-strips in the same belt strip.

In a further step, the belt strips 113 a, 113 b are cut to measure bythe cutting devices 41 a and 41 b in order to obtain the portions 112 a,112 b which will be subsequently superposed on the assembly drums 13 and14.

In this embodiment of the method and since the reinforcing cords 106 ofthe belt strips 113 a and 113 b already have an opposite inclinationwith respect to the conveying directions Y—Y and Z—Z, such superposingstep of the portions 112 a, 112 b is carried out according to thefollowing steps, as illustrated in FIG. 13:

-   i) applying the radially inner belt strip portion 112 a on the first    assembly drum 13, by tangentially feeding the strip portion 112 a at    the bottom of the drum 13;-   ii) switching the two drums 13 and 14 with one another by rotating    of 180° the device 15 for supporting and angularly positioning the    drums about an axis R—R perpendicular to the axis A—A of rotation of    the above-mentioned drums;-   iii) applying the radially outer belt strip portion 112 b on the    radially inner belt strip portion 112 a, by tangentially feeding the    strip portion 112 b at the bottom of the drum 13, thereby forming    the belt structure on the drum positioned in the above-mentioned    assembling position,-   iv) applying a new radially inner belt strip portion 112 a on the    second assembly drum 14, by tangentially feeding the strip portion    112 a at the bottom of the drum 14 and-   v) cyclically repeating steps i) to iv).

The steps i) and iv) may be carried out by tangentially feeding theportions 112 a, 112 b of the belt strips both at the top of the drums 13and 14.

With reference to the above-described plant 1, a method according to theinvention for manufacturing a belt package and a crown structure of agreen tire, will now be illustrated.

In an initial step, the belt structure assembled on the assembly drum 13or 14 placed in the assembling position aligned with the belt 12, ispicked up by the first transfer device 17 and transferred to the thirdassembly drum 18.

In a subsequent step, a layer of rubber mixture having a predeterminedwidth and including a plurality of circumferentially orientedreinforcing cords 104, i.e. zero degree cords, is coaxially formed onthe belt structure supported by the third assembly drum 18.

Preferably, this reinforcing layer has a width substantially equal tothe width of the belt structure and is obtained by spirally winding thetape 103, which is fed in a substantially continuous manner by theproduction line 3, around the belt structure.

As illustrated above, the tape 103 is extruded in a substantiallycontinuous manner by the extrusion head 22, cooled by the rolls 23 andcut to size at the end of the assembling step on the belt structure by ahead with a pneumatic shear cutting mechanism (not shown), so as toobtain the belt package.

The method for manufacturing the crown structure comprises an additionalstep wherein a plurality of treads 105 are prepared in a substantiallycontinuous manner by cutting the substantially continuous tread sheet114 of rubber mixture in portions having a predetermined length alongthe cooled conveyor belt 26.

As illustrated above, the tread 105 is extruded in the form of acontinuous tread sheet 114 from the extrusion head 25 and transported bymeans of the conveyor belt 26 on which the sheet 114 is cut to size by ashearer, conventional per se and not shown.

In a subsequent step, the tread 105 thus obtained is coaxially appliedonto the belt package prepared on the assembly drum, possibly with thehelp of pressing rolls or other means adapted to facilitate theimplementation of this step.

Subsequently, the assembly drum 18 is moved by the positioning device 46from the assembling position D of the belt package and of the crownstructure to the picking-up position G of the crown structure by meansof the second transfer ring 60.

Finally, transfer ring 60 transfers the crown structure thus assembledonto the assembly drum, not shown, where the green tire is completed byassembling the crown structure to a previously prepared tire carcassobtained by assembling together the other semi-finished products (liner,carcass structure, sidewalls, beads, and so on) by means of a shapingoperation of the carcass.

FIGS. 14–21 schematically illustrate additional embodiments of the plant2 for manufacturing the belt structure according to the invention.

In the following description and in said figures, the elements of theplant 2 for manufacturing the belt structure structurally orfunctionally equivalent to those previously illustrated with referenceto FIGS. 1–13 will be indicated by the same reference numbers and willnot be further described.

In an alternative embodiment of the plant 2 illustrated in FIGS. 14–17,the transfer device 27 of the strips 108 includes a strip-conveying belt62 adapted to convey the strips along a conveying axis N—N parallel tothe cutting direction of the sheet 109 of rubber-coated fabric. Saidbelt 62 carries out the same function of the multiple arm carousel 57 ofthe first embodiment.

The plate 50 carries out both the function of dragging the sheet 109 ofrubber-coated fabric for a distance having a predetermined length (equalto the length of the strip to be obtained) past the first cutting device32, and the function of releasing the strip 108 thus obtained onto thebelt 62.

The belt 62 then transfers the strip 108 away from the direction X—X, asillustrated in FIG. 14, shifting the same in a picking-up position H atwhich the strip 108 will be subsequently picked up by the positioningdevice 33 of the half-strips.

The half-strips 107 in excess will be released by said device 33 in thecollection container 67 (FIG. 14).

In an additional embodiment of the plant 2, not shown, theabove-mentioned strip catching means 36 of the positioning device 33 ofthe half-strips includes a pair of coplanar plates, for example ofmagnetic type, slidably mounted on a supporting beam without the help ofa pair of slides.

With reference to the above-mentioned plant, a method according to theinvention for manufacturing a belt structure may be carried out in thefollowing way.

The strip 108, released by the plate 50 on the belt 62 after cutting thesheet 109 of rubber-coated fabric, is transported by the belt 62 alongthe direction N—N. This operation enables to transfer the strip 108 to asuitable picking-up position H by the positioning device 33 of thehalf-strips. This positioning device 33 picks up the strip 108 lying onthe belt 62 at the picking-up position H and transports the strip to therequired cutting position F, optionally rotating the strip 108 of apredetermined angle γ with respect to the direction X—X.

It should be noted that the value of the angle γ may also be equal to 0°depending upon the orientation assumed by the strip 108 in thepicking-up position H and upon the cutting direction of the strip.

In a step following the cutting operation of the strip 108 in twohalf-strips 107, 111, the latter are suitably moved away from each otheralong a direction substantially perpendicular to the cutting directionby means of the plates 38 a, 38 b of the positioning device 33 of thehalf-strips.

Subsequently, the half-strips 107 and 111 thus moved away are releasedby said device 33, upon demagnetization of the plates 38 a, 38 b,respectively on conveyor belts 11 and 12.

In a subsequent step of the method and similarly to what has beendescribed in the first embodiment of the method according to theinvention, the half-strips 107, 110 are butt spliced to each other byapproaching the edges of adjacent half-strips thanks to a longitudinaltraction exerted along the facing edges of the half-strips by the rollsor by the jaws of the splicing device movably supported above theconveyor belts 11 and 12.

Also in this case, the final steps of the method for manufacturing thebelt structure involve the superposing of the portions 112 a, 112 bobtained from the belt strips 113 a and 113 b on the assembly drums 13and 14 in a manner similar to what has been previously described.

In a further and advantageous embodiment, the method according to theinvention involves the preparation of belt strips 113 a, 113 b havingreinforcing cords 106 having the same inclination with respect to therespective conveying directions Y—Y, Z—Z. In this case, the portions ofbelt strips 112 a, 112 b assume the desired configuration in which thecords 106 are inclined in opposite direction with respect to that of thecords of the adjacent strip by suitably feeding the portions of thestrips 112 a, 112 b towards the assembly drums 13, 14.

In this case, the downstream section of one of the conveyor belts 11 and12, for example the section 11 b of the conveyor belt 11, assumes—unlikethe alternative embodiment of the plant 2 previously described—aninclination which enables a tangential supply of the portion of beltstrip 112 a at the bottom of the assembly drum 13 (FIG. 20). The portionof belt strip 112 b, on the other hand, is tangentially fed at the topof the assembly drum 14.

The assembling step of the strip portions 112 a, 112 b to form the beltstructure, is therefore carried out in the following way, as shown inFIG. 21:

-   i) applying the radially inner belt strip portion 112 a on the first    assembly drum 13, by tangentially feeding the strip portion 112 a at    the bottom of the drum 13 and by rotating the drum 13 in a first    direction of rotation about the axis A—A;-   ii) switching the two drums 13 and 14 with one another by rotating    of 180° the device 15 for supporting and angularly positioning the    drums about the axis R—R perpendicular to the rotation axis A—A of    the above-mentioned drums;-   iii) applying the radially outer belt strip portion 112 b on the    radially inner belt strip portion 112 a, in a tangential manner and    at the top of the drum 13, thereby forming the belt structure on the    drum located in the above-mentioned assembling position by rotating    the drum 13 around the axis A—A in the opposite direction with    respect to the above-mentioned first direction of rotation,-   iv) applying a new radially inner belt strip portion 112 a on the    second assembly drum 14, by tangentially feeding the strip portion    112 a at the bottom of the drum 14 and by rotating the drum 14 about    the axis A—A in the above-mentioned first direction of rotation, and-   v) cyclically repeating steps i) to iv).

The method and the plant 9 according to the invention may include anadditional advantageous variant in which the splicing methods of thehalf-strips 107 and 110 enable to form the belt strips 113 a, 113 bwhile reducing as much as possible the strains exerted in longitudinaldirection on the elastomeric material being processed and thisindependently of the inclination that the reinforcing cords 106 of thebelt strips 113 a, 113 b may have with respect to the respectiveconveying directions Y—Y, Z—Z.

Purely as an illustrative and non limiting example, this variant isillustrated with reference to the embodiment wherein the belt strips 113a, 113 b having reinforcing cords 106 presenting the same inclinationwith respect to the respective conveying directions Y—Y, Z—Z areprepared.

More particularly, in this additional embodiment of the plant 2, theextrusion head 7 may be provided with a suitably shaped die adapted toform a sheet 109 of rubber-coated fabric having a lip 70 made ofelastomeric material and having a suitable width.

Thanks to this structural feature of the sheet 109 of rubber-coatedfabric, it is possible to obtain (by carrying out the previouslyillustrated cutting and handling operations) a plurality of half-strips107, 110 provided—at one of the edges to be spliced—with a respectivelip 70 only made of elastomeric material (FIG. 18).

In this embodiment, a seat for receiving with a substantially matingengagement the edge of an adjacent strip 107, 110 is defined above thelip 70, which seat facilitates the butt splicing of the half-strips withthe formation in a substantially continuous manner of the belt strips113 a, 113 b.

Conveniently, the butt splicing devices of the half-strips 107 and110—indicated at 69 in FIG. 19—include in this case a plate 68 ofsuitable size and weight, movably supported above the conveyor belts 11,12. The plate 68 picks up each half-strip, for example the half-strip107, by means of a plurality of magnets 71 and places the half-strip atthe free end of the belt strip 113 a being formed on the conveyor belt11.

In this case, the splicing is carried out by the plate 68 which, bypressing on the entire top surface of each half-strip 107 to be spliced,promotes the engagement and the union by pressure of the edge of thehalf-strip 107 with the lip 70 of the adjacent half-strip 107′ alreadybelonging to the belt strip 113 a being formed.

Advantageously, the butt splicing between subsequent half-strips 107,110 (or, better, between a structurally independent half-strip and thefree end of the belt strip 113 a or 113 b being formed) takes place byexerting a pressure in a direction substantially perpendicular to thelying plane of the belt strip 113 a or 113 b thanks to the action of theplate 68 movably supported above the conveyor belts 11 and 12.

Thanks to these features, it is therefore possible to prepare the beltstrips 113 a, 113 b while reducing as much as possible the strainsexerted in longitudinal direction on the elastomeric material beingprocessed, thereby reducing as much as possible any stress ordeformation which may have a negative influence on the quality of thebelt structure thus produced.

From what it has been described and illustrated above, all theadvantages achieved by the invention and especially those related to thepossibility of assembling a belt structure, a belt package and a crownstructure in an essentially automatic manner with minimum labor andensuring a constant and high quality of these products, are immediatelyapparent.

A man skilled in the art may carry out modifications and variants to theabove-described invention in order to fulfill specific and contingentapplicative requirements, variants and modifications anyhow fallingwithin the scope defined by the subsequent claims.

In this way, for example, the half-strips preparation device 9 may beconstituted by one or more automated units suitably programmed to pickup the strips 108 from the receiving position C downstream of thecutting means 32, to transfer the strips to a suitable cutting deviceand to release the half-strips thus obtained, after having turned upsidedown one of the latter, on the belts 11 and 12 or other suitableconveying means, wherein the belt strips 113 a and 113 b aresubsequently assembled.

1. A method for manufacturing a belt structure for a vehicle tire,comprising: preparing, in a substantially continuous manner, a pluralityof strips along a predetermined conveying direction; preparing, in asubstantially continuous manner, a plurality of half-strips by cuttingeach of the strips along a predetermined cutting direction; buttsplicing, in a substantially continuous manner, respective half-stripsto form belt strips; moving, in a substantially continuous manner, thebelt strips toward at least one assembly drum; and superposing, on theat least one assembly drum, portions of each of the belt strips to forma belt structure; wherein each strip comprises a first predeterminedlength extending along the predetermined conveying direction, whereinthe half-strips comprise a second predetermined length, wherein thehalf-strips are aligned along respective conveying directions, whereineach half-strip incorporates reinforcing cords substantially parallel toone another, wherein the belt strips extend along the respectiveconveying directions, wherein the belt-strip portions compriserespective predetermined lengths, wherein the belt structure comprisesradially superposed belt-strip portions, wherein reinforcing cords ineach belt-strip portion are substantially parallel to one another, andwherein, relative to an equatorial plane of the belt structure, thereinforcing cords in a first belt-strip portion are inclined in anopposite direction with respect to the reinforcing cords in a radiallyadjacent belt-strip portion.
 2. The method of claim 1, furthercomprising: cutting a sheet of rubber-coated fabric along a firstcutting direction forming a first predetermined angle with respect tothe predetermined conveying direction to form the plurality of strips;transferring each strip to a cutting position away from thepredetermined conveying direction; cutting each strip along a secondcutting direction to form two half-strips; and moving the twohalf-strips away from each other along a direction substantiallyperpendicular to the second cutting direction; wherein the sheetincorporates reinforcing cords substantially parallel to one another,and wherein the second cutting direction forms a second predeterminedangle with respect to a longitudinal axis of each strip.
 3. The methodof claim 2, further comprising: turning one of the two half-stripsupside down, so that, relative to the equatorial plane of the beltstructure, reinforcing cords in a first half-strip are inclined in anopposite direction with respect to reinforcing cords in a correspondingsecond half-strip.
 4. The method of claim 1, wherein the half-strips arebutt spliced on conveying means arranged along the respective conveyingdirections.
 5. The method of claim 4, wherein the belt strips are movedtoward the at least one assembly drum by the conveying means.
 6. Themethod of claim 1, wherein superposing portions of each of the beltstrips comprises: cutting out a portion of a first belt strip, theportion of the first belt strip comprising a length substantially equalto a circumferential development of a first assembly drum; cutting out aportion of a second belt strip, the portion of the second belt stripcomprising a length substantially equal to the circumferentialdevelopment of the first assembly drum; applying the portion of thefirst belt strip on the first assembly drum; rotating a device forsupporting and angularly positioning the at least one assembly drum toreposition the first assembly drum; and applying the portion of thesecond belt strip on the portion of the first belt strip to form thebelt structure.
 7. The method of claim 1, wherein superposing portionsof each of the belt strips comprises: cutting out a portion of a firstbelt strip, wherein the portion of the first belt strip comprises alength substantially equal to a circumferential development of a firstassembly drum; cutting out a portion of a second belt strip, wherein theportion of the second belt strip comprises a length substantially equalto the circumferential development of the first assembly drum; applyingthe portion of the first belt strip on the first assembly drum; rotatinga device for supporting and angularly positioning the at least oneassembly drum to reposition the first assembly drum and a secondassembly drum; applying the portion of the second belt strip on theportion of the first belt strip to form the belt structure; andrepeating this groups of actions, as required, alternately on the firstand second assembly drums.
 8. The method of claim 1, wherein superposingportions of each of the belt strips comprises: cutting out a portion ofa first belt strip, wherein the portion of the first belt stripcomprises a length substantially equal to a circumferential developmentof a first assembly drum; applying the portion of the first belt stripon the first assembly drum; rotating through 180° a device forsupporting and angularly positioning the at least one assembly drum toswitch positions of the first assembly drum and a second assembly drum;cutting out a portion of a second belt strip, wherein the portion of thesecond belt strip comprises a length substantially equal to thecircumferential development of the first assembly drum; applying theportion of the second belt strip on the portion of the first belt stripto form the belt structure; and repeating this group of actions, asrequired, alternately on the first and second assembly drums; whereinthe first and second assembly drums are fixed on diametrically oppositesides of the device for supporting and angularly positioning the atleast one assembly drum.
 9. The method of claim 1, further comprising:discarding one of the half-strips as a function of a length increase ofone of the belt strips.
 10. A plant for manufacturing a belt structurefor a vehicle tire, comprising: an extrusion apparatus to form, insubstantially continuous manner, a sheet of rubber-coated fabric; firstconveying means to transport the sheet along a predetermined conveyingdirection; a first device for cutting the sheet along a first cuttingdirection forming a first predetermined angle with respect to thepredetermined conveying direction to form multiple strips; a seconddevice for preparing, from the multiple strips, a plurality of first andsecond half-strips by cutting each strip into two parts along apredetermined cutting direction; second conveying means for transportingthe first and second half-strips along respective conveying directions;a third device for butt splicing the first half-strips to each other andthe second half-strips to each other to form substantially continuousbelt strips on the second conveying means; a fourth device for cuttingthe substantially continuous belt strips into portions; and at least oneassembly drum adapted to support the belt-strip portions; wherein thesheet incorporates reinforcing cords substantially parallel to oneanother, wherein the multiple strips comprise a first predeterminedlength extending along the predetermined conveying direction, whereinthe half-strips comprise a second predetermined length, wherein thehalf-strips are aligned along the respective conveying directions,wherein each half-strip incorporates reinforcing cords substantiallyparallel to one another, and wherein the belt-strip portions compriserespective predetermined lengths.
 11. The plant of claim 10, wherein theextrusion apparatus comprises: an extrusion head for supplying, in asubstantially continuous manner, the sheet of rubber-coated fabric onthe first conveying means; wherein the reinforcing cords of the sheetare supplied by a creel supported in a vicinity of the extrusion head.12. The plant of claim 10, wherein the second device comprises: a fifthdevice; a sixth device; and a seventh device; wherein the fifth devicemoves the strips away from the first conveying means, wherein the fifthdevice also transfers each strip to a cutting position away from thepredetermined conveying direction, wherein the sixth device cuts eachstrip along a second cutting direction to form the first and secondhalf-strips, wherein the second cutting direction forms a secondpredetermined angle with respect to a longitudinal axis of each strip,wherein the seventh device moves the first and second half-strips awayfrom each other along a direction substantially perpendicular to thesecond cutting direction, and wherein the seventh device also positionsthe first and second half-strips on the second conveying means.
 13. Theplant of claim 12, further comprising: an eighth device for turning thefirst half-strips or the second half-strips upside down; wherein theeighth device is disposed downstream of the sixth device.
 14. The plantof claim 13, wherein the eighth device comprises: a plate provided withmeans for catching respective half-strips; wherein the eighth device isdisposed upstream of the second conveying means of the respectivehalf-strips, wherein the plate is rotatably mounted on a respectivesupporting frame, and wherein the frame is guided to and from the secondconveying means of the respective half-strips.
 15. The plant of claim12, wherein the seventh device picks up each of the strips at apicking-up position and rotates each strip a third predetermined anglewith respect to the predetermined conveying direction.
 16. The plant ofclaim 15, wherein the seventh device comprises means for catching thestrips, and wherein the means for catching the strips is rotatablymounted about an axis perpendicular to the strips on a supporting frameguided to and from the sixth device.
 17. The plant of claim 15, whereinthe seventh device comprises: two substantially coplanar plates; andmeans for moving the two plates toward and away from each other; whereineach plate is provided with means for catching the half-strips.
 18. Theplant of claim 12, wherein the fifth device comprises: a carousel;wherein the carousel comprises at least one strip-supporting arm, andwherein the at least one strip-supporting arm is angularly movablebetween a first strip-receiving position located downstream of the firstdevice and a picking-up position.
 19. The plant of claim 18, wherein thecarousel further comprises: a strip-supporting oscillating table hingedto the at least one strip-supporting arm; wherein the oscillating tableis movable to and from the first device.
 20. The plant of claim 12,wherein the fifth device comprises: strip-conveying means; wherein thestrip-conveying means comprises a conveying axis substantially parallelto the first cutting direction, and wherein the strip-conveying means ismovable between a strip-receiving position, located downstream of thefirst device, and a picking-up position.
 21. A method for manufacturinga belt package for a vehicle tire, comprising: preparing, in asubstantially continuous manner, a plurality of strips along apredetermined conveying direction; preparing, in a substantiallycontinuous manner, a plurality of half-strips by cutting each of thestrips along a predetermined cutting direction; butt splicing, in asubstantially continuous manner, respective half-strips to form beltstrips; moving, in a substantially continuous manner, the belt stripstoward at least one assembly drum; superposing, on the at least oneassembly drum, portions of each of the belt strips to form a beltstructure; transferring the belt structure to a separate assembly drum;and coaxially forming on the belt structure, supported by the separateassembly drum, a layer of rubber mixture comprising a plurality ofcircumferentially oriented reinforcing cords; wherein each stripcomprises a first predetermined length extending along the predeterminedconveying direction, wherein the half-strips comprise a secondpredetermined length, wherein the half-strips are aligned alongrespective conveying directions, wherein each half-strip incorporatesreinforcing cords substantially parallel to one another, wherein thebelt strips extend along the respective conveying directions, whereinthe belt-strip portions comprise respective predetermined lengths,wherein the belt structure comprises radially superposed belt-stripportions, wherein reinforcing cords in each belt-strip portion aresubstantially parallel to one another, wherein, relative to anequatorial plane of the belt structure, the reinforcing cords in a firstbelt-strip portion are inclined in an opposite direction with respect tothe reinforcing cords in a radially adjacent belt-strip portion, andwherein the layer of rubber mixture comprises a width substantiallyequal to a width of the belt structure.
 22. The method of claim 21,wherein the layer of rubber mixture is formed by applying a ribbon ofrubber mixture comprising a predetermined width on the belt structure,and wherein the ribbon is coextruded in a substantially continuousmanner with a plurality of reinforcing cords prealigned along adirection parallel to an extrusion direction of the ribbon.
 23. Themethod of claim 21, wherein the layer of rubber mixture is formed byspirally winding on the belt structure at least one tape of rubbermixture incorporating one or more circumferentially oriented reinforcingcords.
 24. A plant for manufacturing a belt package for a vehicle tire,comprising: a first extrusion apparatus to form, in a substantiallycontinuous manner, a sheet of rubber-coated fabric; first conveyingmeans to transport the sheet along a predetermined conveying direction;a first device for cutting the sheet along a first cutting directionforming a first predetermined angle with respect to the predeterminedconveying direction to form multiple strips; a second device forpreparing, from the multiple strips, a plurality of first and secondhalf-strips by cutting each strip into two parts along a predeterminedcutting direction; second conveying means for transporting the first andsecond half-strips along respective conveying directions; a third devicefor butt splicing the first half-strips to each other and the secondhalf-strips to each other to form substantially continuous belt stripson the second conveying means; a fourth device for cutting thesubstantially continuous belt strips into portions; at least oneassembly drum adapted to support the belt-strip portions; a secondextrusion apparatus to form, in a substantially continuous manner, aribbon or tape of rubber mixture incorporating a plurality ofreinforcing cords substantially parallel to one another; means forcutting the ribbon or tape of rubber mixture into portions havingpredetermined length; a separate assembly drum; and a device fortransferring a belt structure comprising at least two of the belt-stripportions toward the separate assembly drum; wherein the sheet ofrubber-coated fabric incorporates reinforcing cords substantiallyparallel to one another, wherein the multiple strips comprise a firstpredetermined length extending along the predetermined conveyingdirection, wherein the half-strips comprise a second predeterminedlength, wherein the half-strips are aligned along the respectiveconveying directions, wherein each half-strip incorporates reinforcingcords substantially parallel to one another, and wherein the belt-stripportions comprise respective predetermined lengths.
 25. The plant ofclaim 24, wherein the second extrusion apparatus comprises an extrusionhead.
 26. A method for manufacturing a crown structure for a vehicletire, comprising: preparing, in a substantially continuous manner, aplurality of strips along a predetermined conveying direction;preparing, in a substantially continuous manner, a plurality ofhalf-strips by cutting each of the strips along a predetermined cuttingdirection; butt splicing, in a substantially continuous manner,respective half-strips to form belt strips; moving, in a substantiallycontinuous manner, the belt strips toward at least one assembly drum;superposing, on the at least one assembly drum, portions of each of thebelt strips to form a belt structure; transferring the belt structure toa separate assembly drum; coaxially forming on the belt structure,supported by the separate assembly drum, a layer of rubber mixturecomprising a plurality of circumferentially oriented reinforcing cords;providing, in a substantially continuous manner, a tread by cutting asubstantially continuous tread sheet of rubber mixture into portionshaving predetermined length; and coaxially applying the tread on thelayer of rubber mixture; wherein each strip comprises a firstpredetermined length extending along the predetermined conveyingdirection, wherein the half-strips comprise a second predeterminedlength, wherein the half-strips are aligned along respective conveyingdirections, wherein each half-strip incorporates reinforcing cordssubstantially parallel to one another, wherein the belt strips extendalong the respective conveying directions, wherein the belt-stripportions comprise respective predetermined lengths, wherein the beltstructure comprises radially superposed belt-strip portions, whereinreinforcing cords in each belt-strip portion are substantially parallelto one another, wherein, relative to an equatorial plane of the beltstructure, the reinforcing cords in a first belt-strip portion areinclined in an opposite direction with respect to the reinforcing cordsin a radially adjacent belt-strip portion, and wherein the layer ofrubber mixture comprises a width substantially equal to a width of thebelt structure.
 27. The method of claim 26, wherein the tread is formedby extrusion in a substantially continuous manner.
 28. A plant formanufacturing a crown structure for a vehicle tire, comprising: a firstextrusion apparatus to form, in a substantially continuous manner, asheet of rubber-coated fabric; first conveying means to transport thesheet along a predetermined conveying direction; a first device forcutting the sheet along a first cutting direction forming a firstpredetermined angle with respect to the predetermined conveyingdirection to form multiple strips; a second device for preparing, fromthe multiple strips, a plurality of first and second half-strips bycutting each strip into two parts along a predetermined cuttingdirection; second conveying means for transporting the first and secondhalf-strips along respective conveying directions; a third device forbutt splicing the first half-strips to each other and the secondhalf-strips to each other to form substantially continuous belt stripson the second conveying means; a fourth device for cutting thesubstantially continuous belt strips into portions; at least oneassembly drum adapted to support the belt-strip portions; a secondextrusion apparatus to form, in a substantially continuous manner, aribbon or tape of rubber mixture incorporating a plurality ofreinforcing cords substantially parallel to one another; first means forcutting the ribbon or tape of rubber mixture into portions havingpredetermined length; a separate assembly drum; a device fortransferring a belt structure comprising at least two of the belt-stripportions toward the separate assembly drum; a third extrusion apparatusto form, in a substantially continuous manner, a continuous tread sheetof rubber mixture; third conveying means for transferring the continuoustread sheet of rubber mixture toward the separate assembly drum; andsecond means for cutting the continuous tread sheet of rubber mixtureinto portions having predetermined length to form a tread; wherein thesheet of rubber-coated fabric incorporates reinforcing cordssubstantially parallel to one another, wherein the multiple stripscomprise a first predetermined length extending along the predeterminedconveying direction, wherein the half-strips comprise a secondpredetermined length, wherein the half-strips are aligned along therespective conveying directions, wherein each half-strip incorporatesreinforcing cords substantially parallel to one another, and wherein thebelt-strip portions comprise respective predetermined lengths.
 29. Theplant of claim 28, wherein the third conveying means is provided withcooling means.